Animation Nodes: How to unzip a list
I'd suggest to use an expression or script node for that. Although an expression should be all you need. Only in case you need to do this in multiple places you should use a script node maybe.

a = [[(0,0,1), (0,0,2)], [(1,0,1), (1,0,2)]]

# long version (for script node maybe)
result = []
for sublist in a:
    result.extend(sublist)

# shorter version (single expression, can be used in the Expression node)
import itertools
result = list(itertools.chain.from_iterable(a))

# you can also use a nested list comprehension
result = [vector for vector in sublist for sublist in a]


To use itertools in the expression node you need to write that into the advanced node settings: